Video phone service means conversing by a phone while viewing a screen provided by a counterpart user through a mobile communication terminal with a camera. As CDMA 1× EV-DO, a WCDMA mobile communication network capable of receiving and transmitting high speed packet data has been commercialized, such video phone service can be provided to a mobile communication service subscriber.
Video phone service is being made based on 3G-324M or CDMA H.323, SIP protocols of WCDMA, and it has an advantage of being able to transferring video and audio together for a phone conversation in contrast to a conventional audio phone conversation, whereas it has a disadvantage of requiring an earphone or a highly efficient speakerphone. Accordingly, if an earphone or a speakerphone is not appropriately prepared, there is a problem that audio cannot accurately be transferred due to noise of in the environment.
To resolve the above problem, if a video phone conversation is unavailable not possible due to noise of in the environment during video phone service, a function capable of transferring a text message to supplement audio message is necessary.
Although there has already been a function to receive a text message during a video phone conversation using an audio/data concurrent service of a mobile telecommunication network, this function is merely to report the fact that a text message is has been received. Accordingly, there is a problem that a video phone conversation should has to be terminated for a mobile telecommunication terminal user to communicate by text message with a counterpart user during a video phone conversation, and there has been not yet prepared a method does not yet exist to transmit and receive a text during a video phone conversation.